This information comes courtesy of the diligent people at Answers.com, who also had many chart-related tidbits...

In 1991, Guns N' Roses scored a feat when the band's albums Use Your Illusion I and Use Your Illusion II debuted at the two highest spots of the Billboard 200, becoming the first act to do this. In 2004, Nelly equalled Guns N' Roses' feat by having his albums Suit and Sweat debut at numbers one and two.

As of 2006, Pink Floyd's Dark Side of the Moon has been on the charts for over 1,500 weeks, or just about twenty-eight years. The album spent 741 of those weeks on the Billboard 200. The other weeks were spent on the Top Pop Catalog Albums chart. Its closest rival is Bob Marley's Legend, checking in at over 800 weeks (Billboard 200 and Top Pop Catalog Albums combined).

Forever Your Girl by Paula Abdul spent sixty-four consecutive weeks on the Billboard 200 before hitting number one, making it the longest time for an album to reach the number one spot.

At one point in early 1980, all nine albums released to that date by Led Zeppelin were on the Billboard 200 chart, the most albums by a single artist to chart at the same time.

The only EP to reach number one on the chart was Alice in Chains' Jar of Flies in 1994.

Also on Mental Floss:

DID YOU KNOW? Marlon Brando hated memorizing lines so much that he posted cue cards everywhere to help him get through scenes.
He even asked for lines to be written on an actress's posterior. (That request was denied.)